1. Field of the Invention
The present invention relates generally to vehicles and, more particularly, to an anti-theft vehicle system used to inhibit rotation of a vehicle wheel outside a predetermined spatial perimeter.
2. Description of the Related Art
It is sometimes desired to contain a vehicle within a predetermined spatial boundary or perimeter. In particular, retail stores are attempting to reduce the amount of lost vehicles such as shopping carts, which are either stolen or taken out of the normal bounds of the stores and not returned.
Accordingly, U.S. Pat. No. 5,194,844 to Zelda discloses a vehicle theft prevention system which inhibits the use of a shopping cart once it is moved outside a boundary. This patented system includes an electronic wire that extends around and defines a perimeter of normal operating space which is used by operators of a store's shopping carts. The electronic wire produces an electromagnetic field which is sensed by a sensor located adjacent one wheel of the shopping cart. The sensor sends a signal to a motor which moves a brake pad against the wheel of the shopping cart. Two limit switches are used to stop the motor when the motor has either moved the brake pad into or out of engagement with the wheel of the shopping cart.
One disadvantage of the above system is that it is relatively expensive because the motor must be large and two limit switches are needed. Another disadvantage of the above system is that an asymmetric time-variant wave form is used for the electromagnetic field which is undesired.